Porphyria cutanea tarda is often severe and difficult to treat when associated with end stage renal disease. Erythropoietin deficiency causes anemia and prevents treatment of these patients by phlebotomy. Erythropoietin administration, which can mobilize excess iron, correct anemia and support phlebotomy, is being studied in 20 patients with this condition, and the effects of erythropoietin treatment on plasma porphyrins and measures of iron status are closely monitored.